Golf ball

ABSTRACT

A golf ball composed of a core and a cover has a spin rate and a launch angle on approach shots at a head speed (HS) of 20 m/s or 10 m/s that satisfy formulas (1) and (2) below: 
       Spin  W/ Spin  D≥0.70    (1)
 
       Ang  W/ Ang  D&lt;1.20    (2)
 
     Here, Spin D is the spin rate (rpm) under dry conditions, Spin W is the spin rate (rpm) under wet conditions, Ang W is the launch angle (°) under wet conditions and Ang D is the launch angle (°) under dry conditions. The golf ball suppresses a decrease in the spin rate on approach shots in rainy weather and thus has an improved controllability, making it especially useful to professional golfers and skilled amateurs who desire a high spin performance around the green.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application. No. 2019-231164 filed in Japan on Dec. 23,2019, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a multilayer golf ball of two or morepieces that has a cover and a cover. More particularly, the inventionrelates to a golf ball capable of suppressing a decrease in the spinrate on approach shots under wet conditions.

BACKGROUND ART

Golf balls, when used under dry, fair weather conditions, achieve asufficient distance on shots with a driver and also incur a suitableamount of spin on approach shots that require controllability, and soare not regarded as problematic. However, golf balls are known to beless receptive to spin and to have decreased controllability under wetconditions during rainy weather. Professional golfers and skilledamateurs in particular desire a high spin performance around the green,regardless of the weather.

Art relating to golf balls that suppress a decrease in the spin rate onapproach shots such as with a short iron during rainy weather—i.e., whenthe ball is wet—is described in, for example, JP-A 2011-72836. JP-A2010-179119, JP-A 2007-296383, JP-A 2002-186686, JP-A 2002-186687, JP-A2019-10190 and JP-A 2019-10191. However, in these golf balls, the spinrate on shots with a driver (W#1) when the ball is wet sometimes ends uprising, which may lower the distance traveled by the ball. Also, thegolf balls disclosed in JP-A 2019-10190 and JP-A 2019-10191 do not takeinto account the variability of the spin rate and launch angle onapproach shots in rainy weather, and so there exists a desire forfurther improvement in ball controllability on approach shots when theball is wet.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a golfball which, rainy weather, when the ball is wet, suppresses a decreasein the distance traveled by the ball due to an increased spin rate ondriver shots and also fully suppresses a decrease in the spin rate onapproach shots, thereby enhancing the controllability.

As a result of extensive investigations, we have found that when a golfball having a core and a cover is fabricated so as to satisfy thefollowing spin rate retention and launch angle retention formulas:

Spin W/Spin D≥0.70   (1)

Ang W/Ang D<1.20   (2),

wherein Spin D is the spin rate (rpm) under dry conditions, Spin W isthe spin rate (rpm) under wet conditions, Ang W is the launch angle (°)under wet conditions and Ang D is the launch angle (°) under dryconditions, the golf ball minimizes the decrease in spin rate onapproach shots in rainy weather—i.e., when wet—and thus has an improvedcontrollability, making it particularly useful to professional golfersand skilled amateurs who desire a high spin performance around thegreen.

Accordingly, in a first aspect, the present invention provides a golfball having a core and a cover, which ball has a spin rate and a launchangle on approach shots at a head speed (HS) of 20 m/s that satisfyformulas (1) and (2) below:

Spin W/Spin D≥0.70   (1)

Ang W/Ang D<1.20   (2),

wherein Spin D is the spin rate (rpm) under dry conditions, Spin W isthe spin rate (rpm) under wet conditions, Ang W is the launch angle (°)under wet conditions and Aug D is the launch angle (°) under dryconditions.

In a second aspect, the invention provides a golf ball having a core anda cover, which ball has a spin rate and a launch angle on approach shotsat a head speed (HS) of 10 m/s that satisfy formulas (1) and (2) below:

Spin W/Spin D≥0.70   (1)

Ang W/Ang D<1.20   (2),

wherein Spin D is the spin rate (rpm) under dry conditions, Spin W isthe spin rate (rpm) under wet conditions, Aug W is the launch angle (°)under wet conditions and Ang D is the launch angle (°) under dryconditions.

In preferred embodiments of the golf balls according to the first andsecond aspects of the invention, the cover has an outermost layer onwhich a coating layer is formed, which coating layer is formed of acoating composition composed primarily of a urethane coating containingboth a base resin comprising a polyester polyol and a curing agentcomprising a polyisocyanate. The coating composition preferably includesfrom 0.1 to 10 parts by weight of a water-repellent additive per 100parts by weight of the base resin, inclusive of a solvent. Thewater-repellent additive may be a fluorine-based water repellent: or anacrylic additive. The acrylic additive may be composed of asilicone-modified acrylate. The fluorine-based water repellent may becomposed of a fluorine-based polymer having an alkyl group chain lengthof 7 or less.

In the urethane coating, it is preferable for hexamethylene diisocyanateto be used as the polyisocyanate, with both an isocyanurate and anadduct of the hexamethylene diisocyanate being used together. The mixingratio of the isocyanurate and the adduct of hexamethylene diisocyanate,expressed as the weight ratio “isocyanarate/adduct,” is preferably from95/5 to 40/60).

Advantageous Effects of the Invention

The golf ball of the invention minimizes the decrease in spin rate onapproach shots in rainy weather when the ball is wet, thus improvingball controllability. This makes the ball especially useful toprofessional golfers and skilled amateurs who desire a high spinperformance around the green.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The objects, features and advantages of the invention will become moreapparent from the following detailed description.

The golf ball of the invention has a core and a cover.

The core may be formed of a known rubber material as the base material.Known base rubbers that are natural rubbers or synthetic rubbers may beused as the base rubber. More specifically, the use of primarily apolybutadiene, especially a cis-1,4-polybutadiene having a cis structurecontent of at least 40%, is recommended. Where desired, a naturalrubber, polyisoprene rubber, styrene-butadiene rubber or the like may beused together with the above-described polybutadiene in the base rubber.

The polybutadiene may be synthesized with a metal catalyst, such as aneodymium or other rare-earth catalyst, a cobalt catalyst or a nickelcatalyst.

Co-crosslinking agents such as unsaturated carboxylic acids and metalsalts thereof, inert fillers such as zinc oxide, barium sulfate andcalcium carbonate, organic peroxides such as dicumyl peroxide and1,1-bis(t-butylperoxy)cyclohexane, and other additives may be includedin the base rubber. Where necessary, commercial antioxidants and thelike may be suitably added as well.

Various types of thermoplastic resins and thermoset resins commonly usedas cover stock in golf balls may be used as the cover-forming material.It is preferable in particular to employ a cover composed primarily of athermoplastic polyurethane or other type of urethane resin (collectivelyreferred to below as “polyurethane”) or a polyurea. Details on these areprovided below.

Polyurethane

The polyurethane has a structure which includes soft segments composedof a polymeric polyol (polymeric glycol) that is a long-chain polyol,and hard segments composed of a chain extender and a polyisocyanate.Here, the polymeric polyol serving as a starting material may be anythat has hitherto been used in the art relating to polyurethanematerials, and is not particularly limited. This is exemplified bypolyester polyols, polyether polyols, polycarbonate polyols, polyesterpolycarbonate polyols, polyolefin polyols, conjugated dienepolymer-based polyols, castor oil-based polyols, silicone-based polyolsand vinyl polymer-based polyols. Specific examples of polyester polyolsthat may be used include adipate-type polyols such as polyethyleneadipate glycol, polypropylene adipate glycol, polybutadiene adipateglycol and polyhexamethylene adipate glycol; and lactone-type polyolssuch as polycaprolactone polyol. Examples of polyether polyols includepoly(ethylene glycol), poly(propylene glycol), poly(tetramethyleneglycol) and poly(methyl tetramethylene glycol). One of these may be usedalone or two or more may be used together.

The long-chain polyol preferably has a number-average molecular weightin the range of 1,000 to 5,000. By using a long-chain polyol having anumber-average molecular weight in this range, golf balls made with apolyurethane composition that have excellent properties, including agood rebound and a good productivity, can be reliably obtained. Thenumber-average molecular weight of the long-chain polyol is morepreferably in the range of 1,500 to 4,000, and even more preferably inthe range of 1,700 to 3,500.

Here and below, “number-average molecular weight” refers to thenumber-average molecular weight calculated based on the hydroxyl valuemeasured in accordance with JIS-K1557.

The chain extender is not particularly limited; any chain extender thathas hitherto been employed in the art relating to polyurethanes may besuitably used. In this invention, low-molecular-weight compounds with amolecular weight of 2,000 or less which have on the molecule two or moreactive hydrogen atoms capable of reacting with isocyanate groups may beused. Of these, preferred use can be made of aliphatic diols having from2 to 12 carbon atoms. Specific examples include 1,4-butylene glycol,1,2-ethylene glycol, 1,3-butanediol, 1,6-hexanediol and2,2-dimethyl-1,3-propanediol. Of these, the use of 1,4-butylene glycolis especially preferred.

Any polyisocyanate hitherto employed in the art relating topolyurethanes may be suitably used without particular limitation as thepolyisoryanate. For example, use can be made of one or more selectedfrom the group consisting of 4,4′-diphenylmethane diisocyanate,2,4-toluene diisocyanate, 2,6-toluene diisocyanate, p-phenylenediisocyanate, xylylene diisocyanate, 1,5-naphthylene diisocyanate,tetramethylxylene diisocyanate, hydrogenated xylylene diisocyanate,dicyclohexylmethane diisocyanate, tetramethylene diisocyanate,hexamethylene diisocyanate, isophorone diisocyanate, norbornenediisocyanate, trimethylhexamethylene diisocyanate,1,4-bis(isocyanatomethyl)cyclohexane and dimer acid diisocyanate.Depending on the type of isocyanate used, crosslinking reactions duringinjection molding may be difficult to control.

The ratio of active hydrogen atoms to isocyanate groups in thepolyurethane-forming reaction may be suitably adjusted within apreferred range. Specifically, in preparing a polyurethane by reactingthe above long-chain polyol, polyisocyanate and chain extender, it ispreferable to use the respective components in proportions such that theamount of isocyanate groups included in the polyisocyanate per mole ofactive hydrogen atoms on the long chain polyol and the chain extender isfrom 0.95 to 1.05 moles.

The method of preparing the polyurethane is not particularly limited.Preparation using, the long-chain polyol, chain extender andpolyisocyanate may be carried out by either a prepolymer process or aone-shot process via a known urethane-forming reaction. Of these, meltpolymerization in the substantial absence of solvent is preferred.Production by continuous melt polymerization using a multiple screwextruder is especially preferred.

It is preferable to use a thermoplastic polyurethane material as thepolyurethane. The thermoplastic polyurethane material may be acommercial product, examples of which include those available under thetrade name Pandex from DIC Covestro Polymer, Ltd., and those availableunder the trade name Resamine from Dainichiseika Color & Chemicals Mfg.Co., Ltd.

Polyurea

The polyurea is a resin composition composed primarily of urea linkagesformed by reacting (i) an isocyanate with (ii) an amine-terminatedcompound. This resin composition is described in detail below.

(i) Isocyanate

Suitable use can be made here of an isocyanate that is employed in theprior art relating to polyurethanes, although the isocyanate is notparticularly limited. Use may be made of isocyanates similar to thosedescribed above in connection with the polyurethane material.

(ii) Amine-Terminated Compound

An amine-terminated compound is a compound having an amino group at theend of the molecular chain. In this invention, the long-chain polyaminesand/or amine curing agents shown below may be used.

A long-chain polyamine is an amine compound which has on the molecule atleast two amino groups capable of reacting with isocyanate groups, andwhich has a number-average molecular weight of from 1,000 to 5,000. Inthis invention, the number-average molecular weight is more preferablyfrom 1,500 to 4,000, and even more preferably from 1,900 to 3,000.Examples of such long-chain polyamines include, but are not limited to,amine-terminated hydrocarbons, amine-terminated polyethers,amine-terminated polyesters, amine-terminated polycarbonates,amine-terminated polycaprolactones, and mixtures thereof. Theselong-chain polyamines may be used singly, or two or more may be used incombination.

An amine curing agent is an amine compound which has on the molecule atleast two amino groups capable of reacting with isocyanate groups, andwhich has a number-average molecular weight of less than 1,000. In thisinvention, the number-average molecular weight is more preferably lessthan 800, and even more preferably less than 600. Specific examples ofsuch amine curing agents include, but are not limited to,ethylenediamine, hexamethylenediamine, 1-methyl-2,6-cyclohexyldiamine,tetrahydroxypropylene ethylenediamine, 2,2,4- and2,4,4-trimethyl-1,6-hexanediamine,4,4′-bis(sec-butylamino)dicyclohexylmethane,1,4-bis(sec-butylamino)cyclohexane, 1,2-bis(sec-butylamino)cyclohexane,derivatives of 4,4′-bis(sec-butylamino)dicyclohexylmethane4,4′-dicyclohexylmethanediamine, 1,4-cyclohexane bis(methylamine),1,3-cyclohexane bis(methylamine), diethylene glycol di(aminopropyl)ether, 2-methylpentamethylenediamine, diaminocyclohexane,diethylenetriamine, triethylenetetramine, tetraethylenepentamine,propylenediamine, 1,3-diaminopropane, dimethylaminopropylamine,diethylaminopropylamine, dipropylenetriamine, imidobis(propylamine),monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine,diisopropanolamine, isophoronediamine,4,4′-methylenebis(2-chloroaniline), 3,5-dimethylthio-2,4-toluenediamine,3,5-dimethylthio-2,6-toluenediamine, 3,5-diethylthio-2,4-toluenediamine,3,5-diethylthio-2,6-toluenediamine,4,4′-bis(sec-butylamino)diphenylmethane and derivatives thereof,1,4-bis(sec-butylamino)benzene, 1,2-bis(sec-butylamino)benzene,N,N′-dialkylaminodiphenylmethane,N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine, trimethylene glycoldi-p-aminobenzoate, polytetramethylene oxide di-p-aminobenzoate,4,4′-methylenebis(3-chloro-2,6-diethyleneaniline),4,4′-methylenebis(2,6-diethylaniline), m-phenylenediamine,p-phenylenediamine and mixtures thereof. These amine curing agents maybe used singly or two or more may be used in combination.

(iii) Polyol

Although not an essential ingredient, in addition to the above-describedcomponents (i) and (ii), a polyol may also be included in the polyurea.The polyol is not particularly limited, but is preferably one that hashitherto been used in the art relating to polyurethanes. Specificexamples include the long-chain polyols and polyol curing agentsmentioned below.

The long-chain polyol may be any that has hitherto been used in the artrelating to polyurethanes. Examples include, but are not limited to,polyester polyols, polyether polyols, polycarbonate polyols, polyesterpolycarbonate polyols, polyolefin-based polyols, conjugated dienepolymer-based polyols, castor oil-based polyols, silicone-based polyolsand vinyl polymer-based polyols. These long-chain polyols may be usedsingly or two or more may be used in combination.

The long-chain polyol has a number-average molecular weight ofpreferably from 1,000 to 5,000, and more preferably from 1,700 to 3,500,in this number-average molecular weight range, an even better reboundand productivity are obtained.

The polyol curing agent is preferably one that has hitherto been used inthe art relating to polyurethanes, but is not subject to any particularlimitation. In this invention, use may be made of a low-molecular-weightcompound having on the molecule at least two active hydrogen atomscapable of reacting with isocyanate groups, and having a molecularweight of less than 1,000. Of these, the use of aliphatic diols havingfrom 2 to 12 carbon atoms is preferred. Specific examples include1,4-butylene 1,2-ethylene glycol, 1,3-butanediol, 1,6-hexanediol and2,2-dimethyl-1,3-propanediol. The use of 1,4-butylene glycol isespecially preferred. The polyol curing agent has a number-averagemolecular weight of preferably less than 800, and more preferably lessthan 600.

A known method may be used to produce the polyurea. A prepolymerprocess, a one-shot process or some other known method may be suitablyselected for this purpose.

Resin materials other than the above resin ingredients may also beincluded for such purposes as to further enhance the flowability of thegolf ball resin composition and increase such ball properties as therebound and scuff resistance.

Examples of other resin materials that may be used include polyesterelastomers, polyamide elastomers, ionomer resins,ethylene-ethylene/butylene-ethylene block copolymers and modified formsthereof, polyacetals, polyethylenes, nylon resins, methacrylic resins,polyvinyl chlorides, polycarbonates, polyphenylene ethers, polyarylates,polysulfones, polyethersulfones, polyetherimides and polyamideimides.These may be used singly or two or more may be used together.

The above cover-forming resin composition may include an isocyanatecompound. By including an isocyanate compound, due to reactions betweenthe polyurethane or polyurea serving as the base resin and theisocyanate compound, not only can the scuff resistance of this resincomposition be further enhanced, the flowability increases on account ofthe plasticizing effect of the isocyanate, enabling the moldability tobe enhanced.

Any isocyanate compound employed in conventional polyurethanes may beused without particular limitation as the above isocyanate compound. Forexample, aromatic isocyanate compounds that may be used include2,4-toluene diisocyanate, 2,6-toluene diisocyanate and mixtures of both,4,4-diphenylmethane diisocyanate, m-phenylene diisocyanate and4,4′-biphenyl diisocyanate. Use can also be made of the hydrogenatedforms of these aromatic isocyanate compounds, such asdicyclohexylmethane diisocyanate. Other isocyanate compounds that may beused include aliphatic diisocyanates such as tetramethylenediisocyanate, hexamethylene diisocyanate (HDI) and octamethylenediisocyanate; and alicyclic diisocyanates such as xylene diisocyanate.Further examples of isocyanate compounds that may be used includeblocked isocyanate compounds obtained by reacting the isocyanate groupson a compound having two or more isocyanate groups on the ends with acompound having active hydrogens, and uretdiones obtained by thedimerization of isocyanate.

The amount of the above isocyanate compounds included per 100 parts byweight of the polyurethane or polyurea resin is preferably at least 0.1part by weight, and more preferably at least 0.5 part by weight. Theupper limit is preferably not more than 30 parts by weight, and morepreferably not more than 20 parts by weight. When too little isincluded, a sufficient crosslinking reaction may not be obtained and anincrease in the properties may not be observable. On the other hand,when too much is included, discoloration over time due to heat andultraviolet light may increase, or problems such as a loss ofthermoplasticity or a decline in resilience may arise.

In addition, optional additives may be suitably included in the aboveresin composition according to the intended use thereof. For example,when this resin composition is to be used as a cover material, variousadditives, such as inorganic fillers, organic staple fibers, reinforcingagents, crosslinking agents, pigments, dispersants, antioxidants,ultraviolet absorbers and light stabilizers, may be added to the aboveingredients. When such additives are included, the amount thereof per100 parts by weight of the base resin is preferably at least 0.1 part byweight, and more preferably at least 0.5 part by weight, but preferablynot more than 10 parts by weight, and more preferably not more than 4parts by weight.

The method of molding the cover may involve, for example, feeding theabove resin composition into an injection molding machine and moldingthe cover by injecting the molten resin composition over the core. Inthis case, the molding temperature differs according to the type ofpolyurethane or polyurea, but is typically in the range of 150 to 270°C.

At least one intermediate layer may be placed between the core and thecover. In this case, various types of thermoplastic resins, especiallyionomeric resins, that are used as golf ball cover materials may besuitably used as the intermediate layer material. A commercial productmay be used as the ionomeric resin. Alternatively, the resin materialused in the intermediate layer may be one obtained bye blending, ofcommercially available ionomeric resins, a high-acid ionomeric resinhaving an acid content of at least 16 wt % with an ordinary ionomericresin. With such a blend, a good distance on shots with a driver (W#1)can be obtained due to a high rebound and a reduced spin rate. Theamount of unsaturated carboxylic acid included (acid content) in such ahigh-acid ionomeric resin is typically at least 16 wt %, preferably atleast 17 wt %. and more preferably at least 18 wt %. The upper limit ispreferably 22 wt % or less, more preferably 21 wt % or less, and evenmore preferably 20 wt % or less.

It is desirable to abrade the surface of the intermediate layer in orderto increase adhesion between the intermediate layer material and thepolyurethane resin composition that is preferably used in the covermaterial. Moreover, it is desirable to apply a primer (adhesive) to thesurface of the intermediate layer following such abrasion treatment orto add an adhesion reinforcing agent to the intermediate layer material.

The intermediate layer has a material hardness on the Shore D hardnessscale of preferably at least 61, more preferably at least 62, and evenmore preferably at least 63. The upper limit is preferably not more than72, more preferably not mote than 70, and even more preferably not morethan 68. When the intermediate layer is softer than this range, the ballrebound on full shots with a driver (W#1) or an iron may be inadequateor the ball may be too receptive to spin, as a result of which a gooddistance may not be achieved. On the other hand, when the intermediatelayer is harder than the above range, the durability of the ball tocracking on repealed impact may worsen or the feel at impact may becometoo hard.

The intermediate layer has a thickness which is preferably at least 0.8mm, more preferably at least 1.0 mm, and even more preferably at least1.1 mm. The upper limit is preferably not more than 1.7 mm, and morepreferably not more than 1.5 mm. Outside of this range, the spinrate-lowering effect on driver (W#1) shots may be inadequate and so agood distance may not be achieved.

Numerous dimples may be formed on the outside surface of the coverserving as the outermost layer. The number of dimples arranged on thecover surface, although not particularly limited, is preferably at least250, more preferably at least 300, and even more preferably at least320. The upper limit is preferably not more than 440, more preferablynot more than 400, and even more preferably not more than 360. When thenumber of dimples is higher than this range, the ball trajectory maybecome lower and the distance traveled by the ball may decrease. On theother hand, when the number of dimples is lower that this range, theball trajectory may become higher and a good distance may not beachieved. The arrangement of these dimples may have symmetry thatfollows a tetrahedral, octahedral, dodecahedral or otherpolyhedral/polygonal shape, or may have rotational symmetry along anaxis connecting the poles of the ball.

It is recommended that preferably two or more dimple types, and morepreferably three or more dimple types, of mutually differing diameterand/or depth be formed. With regard to the planar shapes of the dimples,a single dimple shape or a combination of two or more dimple shapes,such as circular shapes, various polygonal shapes, dewdrop shapes andoval shapes, may be suitably used. For example, when circular dimplesare used, the dimple diameter may be set to at least about 2.5 mm and upto about 6.5 mm, and the dimple depth may be set to at least 0.07 mm andup to 0.30 mm. The cross-sectional shapes of the dimples may be definedas one or a combination of two or more types, including arcuate shapes,conical shapes, flat-bottomed shapes and curves expressed by variousfunctions, and may have, other than near the dimple edges, a pluralityof inflection points.

In order for the aerodynamic properties to be fully manifested, it isdesirable for the dimple coverage ratio, i.e., the dimple surfacecoverage SR, which is the collective surface area of the imaginaryspherical surfaces circumscribed by the edges of the individual dimples,as a percentage of the spherical surface area of the golf ball, to beset to at least 70% and not more than 90%. Also, to optimize the balltrajectory, it is desirable for the value V₀, defined as the spatialvolume of the individual dimples below the flat plane circumscribed bythe dimple edge, divided by the volume of the cylinder whose base is theflat plane and whose height is the maximum depth of the dimple from thebase, to be set to at least 0.35 and not more than 0.80. Moreover, it ispreferable for the ratio V_(R) of the sum of the volumes of theindividual dimples, each formed below the flat plane circumscribed bythe edge of the dimple, with respect to the volume of the ball spherewere the ball to have no dimples on its surface, to be set to at least0.6% and not more than 1.0%. Outside of the above ranges in theserespective values, the resulting trajectory may not enable a gooddistance to be achieved and so the ball may fail to travel a fullysatisfactory distance. Also, to satisfy the rule for symmetry of theball's carry, dimple volumes near the poles may be made smaller, anddimple volumes near the equator may be made larger, than the volumes ofdimples away from the poles and the equator.

A coating layer may be formed on the cover surface serving as theoutermost layer. This coating layer can be applied using any of varioustypes of coatings. Given the need for the coating to endure the harshconditions of golf ball use, it is preferable to use a coatingcomposition made up primarily of a urethane coating composed of a polyoland a polyisocyanate.

Polyols that may be used in the coating composition are not particularlylimited and include, for example, acrylic polyols and polyester polyols.These polyols encompass also modified forms thereof. Other polyols mayalso be added in order to increase the ease of the coating operation.

One type of polyester polyol may be suitably used as the polyolcomponent, or two types of polyester polyol may be used together, inwhich case the two types of polyester polyols are designated ascomponent A and component B. These two types of polyester polyol havediffering weight-average molecular weights (Mw), the weight-averagemolecular weight of component A being preferably from 20,000 to 30,000and the weight-average molecular weight of component B being preferablyfrom 800 to 1,500. The weight-average molecular weight of component A ismore preferably from 22,000 to 29,000, and even more preferably from23,000 to 28,000. The weight-average molecular weight of component B ismore preferably from 900 to 1,200, and even more preferably from 1,000to 1,100.

The two types of polyester polyol can be obtained by thepolycondensation of a polyol with a polybasic acid. Examples of thepolyol include diols such as ethylene 1,2-propanediol, 1,3-propanediol,1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol,diethylene glycol, dipropylene glycol, hexylene glycol,dimethylotheptane, polyethylene glycol and polypropylene glycol, as wellas triols, tetraols, and polyols having an alicyclic structure. Examplesof the polybasic acid include aliphatic dicarboxylic acids such assuccinic acid, adipic acid, sebacic acid, azelaic acid and dimer acid;aliphatic unsaturated dicarboxylic acids such as fumaric acid, maleicacid, itaconic acid and citraconic acid; aromatic polycarboxylic acidssuch as phthalic acid, isophthalic acid, terephthalic acid, trimelliticacid and pyromellitic acid, dicarboxylic acids having an alicyclicstructure, such as tetrahydrophthalic acid, hexahydrophthalic acid,1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid andendomethylene tetrahydrophthalic acid; and tris-2-carboxyethylisocyanurate. In particular, a polyester polyol in which a cyclicstructure has been introduced onto the resin backbone may be used as thepolyester polyol serving as component A. Examples include polyesterpolyols obtained by the polycondensation of a polyol having alicyclicstructure, such as cyclohexane dimethanol, with a polybasic acid; andpolyester polyols obtained by the polycondensation of a polyol having analicyclic structure with a diol or triol and a polybasic acid. Apolyester polyol having a hyperbranched structure may be used as thepolyester polyol serving as component B. Examples include polyesterpolyols having a branched structure, such as NIPPOLAN 800, from TosoliCorporation.

The weight-average molecular weight (Mw) of the overall base resincomposed of the above two types of polyester polyol is preferably from13,000 to 23,000, and more preferably from 15,000 to 22,000. Thenumber-average molecular weight (Mn) of the overall base resin composedof the above two types of polyester polyol is preferably from 1,100 to2,000, and more preferably from 1,300 to 1,850. If these averagemolecular weights (Mw and Mn) fall outside of the above ranges, the wearresistance of the coating layer may decrease. The weight-averagemolecular weight and number-average molecular weight arepolystyrene-equivalent values measured by gel permeation chromatography(GPC) using detection with a differential refractometer.

The contents of these two types of polyester polyol (components A and B)are not particularly limited, although it is preferable for thecomponent A content to be from 20 to 30 wt % and the component B contentto be from 2 to 18 wt % of the overall base resin.

In cases where one type of polyester polyol is used, of the two abovetypes of polyester polyol (components A and B), it is preferable to usethe polyester polyol of component A.

As for the polyisocyanate, although not particularly limited, anaromatic, aliphatic, alicyclic or other polyisocyanate is commonly used.Specific examples include tolylene diisocyanate, diphenylmethanediisocyanate, xylylene diisocyanate, tetramethylene diisocyanate,hexamethylene diisocyanate, lysine diisocyanate, isophoronediisocyanate, 1,4-cyclohexylene diisocyanate, naphthalene diisocyanate,trimethylhexamethylene diisocyanate, dicyclohexylmethane diisocyanateand 1-isocyanto-3,3,5-trimethyl-4-isocyanatomethylcyclohexane. These maybe used singly or in admixture.

Modified forms of hexamethylene diisocyanate include, for example,polyester-modified hexamethylene diisocyanate and urethane-modifiedhexamethylene diisocyanate. Derivatives of hexamethylene diisocyanateinclude isocyanurates, biurets and adducts of hexamethylenediisocyanate. Using the hexamethylene diisocyanate is preferable fromthe standpoint of obtaining a thermoplastic urethane coating layer ofexcellent yellowing resistance and flexibility.

By using both an adduct having excellent flexibility and a relativelytough isocyanurate as the hexamethylene diisocyanate (HMDI), a high spinperformance can be obtained in the golf ball. As used herein, “adduct”refers to an addition product of diisocyanate and trimethylolpropane,and “isocyanurate” refers to a diisocyanate trimer.

A commercial product may be used as the hexamethylene diisocyanate(HMDI) isocyanurate. Illustrative examples include Corollate® 2357(Tosoh Corporation), Sumidur N3300 (Sumika Covestro Urethane Co., Ltd,),Duranate™ TPA-100 (Asahi Kasei Corporation), Takenate™ D170N andTakenate™ D177N (both from Mitsui Chemicals, Inc.), and Burnock DN-980(DIC Corporation).

A commercial product may be used as the hexamethylene diisocyanate(HMDI) adduct. Illustrative examples include Coronate® HL (TosohCorporation), Takenate™ D160N (Mitsui Chemicals, Inc.), Duranate™E402-80B and Duranate™ E405-70B (both from Asahi Kaset Corporation, andBurnock DN-955 and Burnock DN-955S (both from DIC Corporation).

As subsequently described, from the standpoint of obtaining the desiredspin rate retention and launch angle retention under wet conditions, themixing ratio of hexamethylene diisocyanate isocyanurate andhexamethylene diisocyanate adduct, expressed as the weight ratioisocyanurate/adduct, is preferably from 95/5 to 40/60, and morepreferably from 80/20 to 55/45.

The molar ratio of hydroxyl groups (OH) on the polyester polyol toisocyanate groups (NCO) on the polyisocyanate, expressed as NCO/OH, ispreferably at least 0.6, and more preferably at least 0.65. The upperlimit is preferably 1.5 or less, more preferably 1.0 or less, and evenmore preferably 0.9 or less. When this molar ratio is lower than 0.6,unreacted hydroxyl groups may remain and the performance and waterresistance as a golf ball coating layer may worsen. On the other hand,when the molar ratio is greater than 1.5, the large excess of isocyanategroups may react with moisture to form fragile urea bonds, as a resultof which the performance of the golf ball coating layer may decline.

An amine catalyst or an organometallic catalyst may be used as thecuring, catalyst (organometallic compound). A metallic soap of aluminum,nickel, zinc, tin or the like that has hitherto been compounded as acuring agent for two-part curable urethane coatings may be suitably usedas this organometallic compound.

Known compounding ingredients for coatings may be optionally included inthe coating composition. For example, thickeners, ultraviolet absorbers,fluorescent whiteners, slip agents and pigments may be suitablyincluded.

In the practice of the invention, as subsequently described, in order toobtain the desired spin rate retention and launch angle retention underwet conditions, it is preferable to include a water-repellent additive.Examples of water-repellent additives that may be used include, withoutparticular limitation, silicone resins, silicone fluids, siliconerubbers, fluorocarbon surfactants, acrylic additives and hydrophobicsilicas, as well as combinations of these. The acrylic additive,although not particularly limited, may be a silicone-modified acrylate.As used herein, a “silicone-modified acrylate” refers to a surfaceconditioner in which a silicone structure has been incorporated into theacrylate backbone of the molecule. When a polysiloxane chain is attachedto the acrylic backbone, unlike conventional polyrotaxane-typesilicones, slip does not readily occur even when the amount of additionis increased, enabling the water repellency to be enhanced. Examples ofsilicone-modified acrylates include those available under the tradenames BYK 3550 and BYK 3700 (both from BYK-Chemie GmbH), and 8BS Series(Taisei Chemical). Exemplary silicone fluids include methyl hydrogensilicone fluids and dimethyl silicone fluids.

Fluorocarbon surfactants are able to achieve a high water repellency ata smaller amount of addition than ordinary hydrocarbon-based surfactantsand silicone-based surfactants. Exemplary fluorocarbon surfactantsinclude, without particular limitation, tetrafluoroethylene andpolytetrafluoroethylene. Fluorocarbon surfactants having perfluoroalkylgroups with an alkyl group chain length of 7 or less are especiallypreferred. Specific examples of such fluorocarbon surfactants includethose available under the trade names S-242, S-243, S-420 and S-421 (allfrom AGC Seimi Chemical Co., Ltd.).

The water-repellent additive is preferably used by adding it to thepolyol component serving as the base resin. The content of thewater-repellent additive relative to the overall base resin (100 wt %)is preferably at least 0.05 wt %, and more preferably at least 0.1 wt %,but preferably not more than 10 wt %, and more preferably not more than5 wt %.

When the above coating composition is used, a coating layer can beformed on the surface of a conventionally manufactured golf ball byfirst preparing the coating composition at the time of application,applying the coating composition onto the ball surface via aconventional painting step and then drying the applied composition in adrying step. Although not particularly limited, preferred use can bemade of spray painting, electrostatic painting or dipping as the methodof application.

As described above, the coating composition for golf balls uses a polyolcomponent as the base resin and a polyisocyanate as the curing agent.Depending on the painting conditions, various organic solvents may bemixed in. Such organic solvents include aromatic solvents such astoluene, xylene and ethylbenzene; ester solvents such as ethyl acetate,butyl acetate, propylene glycol methyl ether acetate and propyleneglycol methyl ether propionate; ketone solvents such as acetone, methylethyl ketone, methyl isobutyl ketone and cyclohexanone; ether solventssuch as diethylene glycol dimethyl ether, diethylene glycol diethylether and dipropylene glycol dimethyl ether; alicyclic hydrocarbonsolvents such as cyclohexane, methylcyclohexane and ethylcyclohexane;and petroleum hydrocarbon solvents such as mineral spirits.

The above drying step may be the same as for known two-part curableurethane coatings. The coating composition of the invention may be driedat a drying temperature of at least about 40° C., and especially between40° C. and 60° C., and for a drying period of 20 to 90 minutes,especially 40 to 50 minutes.

The coating layer thickness, although not particularly limited, ispreferably from 3 to 50 μm, and more preferably from 5 to 20 μm.

It is critical for the golf ball according to the first aspect of theinvention to have a spin rate and a launch angle on approach shots at ahead speed (HS) of 20 m/s that satisfy formulas (1) and (2) below:

Spin W/Spin D≥0.70   (1)

Ang W/Ang D<1.20   (2).

In the formulas, Spin D represents the spin rate (rpm) under dryconditions, Spin W represents the spin rate (rpm) under wet conditions,Ang W represents the launch angle (°) under wet conditions and Ang Drepresents the launch angle (°) under dry conditions.

The “Spin W/Spin D” ratio represents the spin rate retention. The closerthis ratio is to 1.0, the smaller the amount of decrease in the spinrate under wet conditions and the easier the ball is to control, whichis desirable. On the other hand, when this ratio has a small value, theamount of decrease in the spin rate under wet conditions becomes large,making the ball more difficult to control, which is undesirable. Thisvalue must be at least 0.70, and is preferably at least 0.75. and morepreferably at least 0.80.

Also, the “Ang W/Ang D” ratio represents the launch angle retention. Thecloser this ratio is to 1.0, the smaller the rise in the launch angleunder wet conditions and the easier it is to adjust the distancetraveled by the ball, which is desirable. On the other hand, when thisratio has a large value, the rise in the launch angle under wetconditions becomes large, making it more difficult to adjust thedistance traveled by the ball, which is undesirable. This value must beless than 1.20, and is preferably 1.15 or less, and more preferably 1.10or less.

It is critical for the golf ball according to the second aspect of theinvention to have a spin rate and a launch angle on approach shots at ahead speed (HS) of 10 m/s that satisfy formulas (1) and (2) below:

Spin W/Spin D≥0.70   (1)

Ang W/Ang D<1.20   (2).

The golf ball of the invention can be made to conform to the Rules ofGolf for play and may be formed to a diameter which is such that theball does not pass through a ring having an inner diameter of 42.672 mmand is not more than 42.80 mm, and to a weight which is preferablybetween 45.0 and 45.93 g.

EXAMPLES

The following Examples and Comparative Examples are provided toillustrate the invention, and are not intended to limit the scopethereof.

Examples 1 to 4, Comparative Examples 1 to 6

A core-forming rubber composition formulated as shown in Table 1 for therespective Examples in Examples 1, 2 and Comparative Examples 1 to 3 wasprepared and then molded and vulcanized to produce a 38.65 mm diametercore. In Examples 3, 4, a core-forming rubber composition formulated asshown in Table 1 is prepared and then molded and vulcanized to produce a38.65 mm diameter core.

TABLE 1 A B Core Polybutadiene 100 100 formulation Unsaturated metal37.4 34.1 (pbw) carboxylate Organic peroxide 1.0 1.0 Antioxidant 0.1 0.1Zinc oxide 14.5 15.8 Zinc salt of 0.0 0.0 pentachlorothiophenol Water0.6 0.6 Vulcanization Temperature (° C.) 152 152 conditions Time (min)19 19

Details on the above core material are given below.

-   Polybutadiene: Available under the Linde name “BR 01” from JSR    Corporation-   Unsaturated metal carboxylate:    -   Zinc acrylate (from Wako Pure Chemical Industries, Ltd.)-   Organic peroxide: Dicumyl peroxide, available under the trade name    “Percumyl D” from NOF Corporation-   Antioxidant: Available under the trade name “Nocrac NS6” from Ouchi    Shinko Chemical Industry Co., Ltd.-   Zinc oxide: Available as “Zinc Oxide Grade 3” from Sakai Chemical    Co., Ltd.-   Zinc salt of pentachlorothiophenol:    -   Available from Wako Pure Chemical Industries, Ltd.-   Water: distilled water (Wako Pure Chemical Industries, Ltd.)

Next, intermediate layer-forming resin material No. 1 or No. 2 shown inTable 2 was injection-molded over the core, thereby producingintermediate layer-encased spheres having a 1.2 mm thick intermediatelayer.

Cover materials No. 3 to No. 5 shown in Table 2 were theninjection-molded over the intermediate layer-encased spheres, therebyproducing three-piece golf balls having a 0.8 mm-thick cover (outermostlayer). Dimples common to all of the Examples were formed at this timeon the surface of the ball cover in each Example.

In Examples 3, 4, an intermediate layer and a cover are formed by thesame way as described above, thereby producing three-piece golf ballshaving a 0.8 mm-thick cover (outermost layer). A plurality of givendimples common to all the Examples and Comparative Examples are formedat this time on the surface of the cover.

TABLE 2 Resin component Acid content (pbw) (wt %) No. 1 No. 2 No. 3 No.4 No. 5 AM 7318 18 85 Himilan 1706 15 35 Himilan 1557 12 15 15 Himilan1605 15 50 Polyurethane (1) 100 Polyurethane (2) 100 Polyurethane (3)100 Trimethylolpropane (TMP) 1.1 1.1 Shore D hardness 65 64 43 47 50

Trade names for the chief materials in this table are given below.

-   AM 7318, Himilan 1706,Himilan 1557, Himilan 1605:    -   Ionomers available from Dow-Mitsui Polychemicals Co., Ltd.-   Polyurethane (1): Ether-type thermoplastic polyurethane available    from DIC Covestro Polymer, Ltd.; Shore D hardness, 43-   Polyurethane (2): Ether-type thermoplastic polyurethane available    from DIC Covestro Polymer, Ltd.; Shore D hardness, 47-   Polyurethane (3): Ether-type thermoplastic polyurethane available    from DIC Covestro Polymer, Ltd:, Shore D hardness, 50    Formation of Coating layer

Next, in each Example, a coating; formulated as shown in Table 3 belowwas applied with an air spray gun onto the surface of the outermostlayer on which numerous dimples had been formed, thereby producing golfballs having a 15 μm-thick coating layer formed thereon.

In Examples 3, 4, a coating is applied onto the surface of the outermostlayer as the same way as the above description, thereby producing golfballs having a 15 μm-thick coating layer formed thereon.

TABLE 3 Coating formulation (pbw) I II III IV V Base resin Polyesterpolyol 27.5 27.5 27.5 27.5 27.5 Additive Type a a b — c Amount added 1.95  0.5  1.95 none  0.5 Organic solvent 72.5 72.5 72.5 72.5 72.5(total) (100)   (100)   (100)   (100)   (100)   Curing agent Isocyanate51.5 51.5 51.5 51.5 51.5 Isocyanurate/adduct (90/10) (90/10) (90/10)(90/10) (100/0) (relative proportions) Organic solvent 48.5 48.5 48.548.5 48.5 (total) (100)   (100)   (100)   (100)   (100)  

Polyester Polyol Synthesis Example

A reactor equipped with a reflux condenser, a dropping funnel, a gasinlet and a thermometer was charged with 140 parts by weight oftrimethylolpropane, 95 parts by weight of ethylene glycol, 157 parts byweight of adipic acid and 58 parts by weight of1,4-cyclohexanedimethanol. The temperature was then raised to between200 and 240° C. under stirring and the reaction was effected by 5 hoursof heating, after which a polyester polyol having an acid value of 4, ahydroxyl value of 170 and a weight average molecular weight (Mw) of28,000 was obtained. Next, the polyester polyol thus synthesized wasdissolved in butyl acetate and the concentration of the polyester polyolcomponent was adjusted to 27.5%.

With regard to the additive in Table 3, the water-repellent additivesused were all commercial products. “Type a” was an acrylic additive (asilicone-modified acrylate available as BYK 3700 from BYK-Chemie GmbH).“Type b” was a fluorine-based water repellent (a fluorocarbon surfactanthaving perfluoroalkyl groups); a fluorine-based polymer having an alkylgroup chain length of 7 or less was added. “Type c” was a silicone-basedadditive (a polyester-modified polysiloxane available as BYK 370 fromBYK-Chemie GmbH).

As for the curing agent in Table 3, using Duranate™ TPA-100 (NCOcontent, 23.1%; nonvolatiles content, 100%) from Asahi Kasei Corporationas the hexamethylene diisocyanate (HMDI) isocyanurate and Daranate™E402-80B (NCO content, 7.6%; nonvolatiles content, 80%) from Asahi KaseiCorporation as the HMDI adduct, these were included in the relativeproportions shown in the table. The curing agent was adjusted to apolyisocyanate component concentration of 51.5% by subsequently addingN-butyl acetate as the organic solvent.

Commercial golf balls were used without modification in ComparativeExamples 4 to 6. The names of these commercial balls were as follows.

-   Comparative Example 4: TITLEIST PRO VI X (2019 model), manufactured    by the Acushnet Company-   Comparative Example 5: SRIXON Z-Star XV (2019 model), a manufactured    by Dunlop-   Comparative Example 6: CALLAWAY CHROME SOFT X (2018 model),    manufactured by the Callaway Golf Company

Evaluation of Spin Rate and Launch Angle on Approach Shots

The spin rate, launch angle and initial velocity of the golf ball underdry conditions and wet conditions were measured. Dry conditions involvedhitting an ordinary golf ball. Wet conditions involved preparing abeaker filled with water, dipping the golf ball in this water and thenhitting the ball in this water-wetted state (representing the ball inrainy weather).

The spin rate and launch angle of each of the dry-condition golf ballsand wet-condition golf bails when struck at head speeds of 20 m/s and 10m/s with a sand wedge (SW) mounted on a golf swing robot were measured,and the spin rate retention ratio and launch angle retention ratio wereevaluated based on the criteria described below. Measurement was carriedout with an apparatus for measuring the initial conditions immediatelyafter the ball was struck. The sand wedge used was the TourB XW-1 (loftangle, 58°) manufactured by Bridgestone Sports Co., Ltd. The results areshown in Table 4 below.

Evaluation Criteria:

-   (1) Spin Rate Retention Ratio    -   Good: Spin rate retention ratio was at least 4.70 and up to 1.00    -   NG: Spin rate retention ratio was less than 0.70-   (2) Launch Angle Retention Ratio    -   Good: Launch angle retention ratio was at least 1.00 but less        than 1.20    -   NG: Launch angle retention ratio was 1.20 or more

TABLE 4 Example Comparative Example 1 2 3 4 1 Ball layers Coating layerI I II III IV Outermost layer No. 4 No. 3 No. 4 No. 4 No. 4 Intermediatelayer No. 1 No. 2 No. 1 No. 1 No. 1 Core A B A A A Sand wedge DRYInitial velocity (m/s) 17 17 17 17 17 evaluation Launch angle (deg) 33.432.9 33.0 33.0 32.7 (HS, 20 m/s) Spin rate (rpm) 6,524 6,613 6,569 6,5696,598 WET Initial velocity (m/s) 17 17 17 17 17 Launch angle (deg) 33.433.2 38.1 35.7 40.0 Spin rate (rpm) 6,420 6,598 4,926 5,762 4,288 Spinrate Ratio 0.98 1.00 0.75 0.88 0.65 retention Rating good good good goodNG Launch Ratio 1.01 1.01 1.16 1.08 1.22 angle Rating good good goodgood NG retention Sand wedge DRY Initial velocity (m/s) 9 9 9 9 9evaluation Launch angle (deg) 34.9 34.8 34.9 34.9 35.0 (HS, 10 m/s) Spinrate (rpm) 3,545 3,645 3,595 3,595 3,557 WET Initial velocity (m/s) 9 99 9 8 Launch angle (deg) 39.4 37.6 40.5 38.5 45.4 Spin rate (rpm) 2,7593,121 2,600 2,940 1,728 Spin rate Ratio 0.78 0.86 0.72 0.82 0.49retention Rating good good good good NG Launch Ratio 1.13 1.08 1.16 1.111.30 angle Rating good good good good NG retention Comparative Example 23 4 5 6 Ball layers Coating layer IV V — — — Outermost layer No. 3 No. 5— — — Intermediate layer No. 2 No. 2 — — — Core B A — — — Sand wedge DRYInitial velocity (m/s) 17 17 17 17 17 evaluation Launch angle (deg) 33.033.0 33.1 32.9 32.7 (HS, 20 m/s) Spin rate (rpm) 6,614 6,416 6,464 6,5006,562 WET Initial velocity (m/s) 17 17 17 17 17 Launch angle (deg) 42.640.8 39.7 41.9 41.9 Spin rate (rpm) 3,452 3,975 4,371 3,664 3,565 Spinrate Ratio 0.52 0.62 0.68 0.56 0.54 retention Rating NG NG NG NG NGLaunch Ratio 1.29 1.24 1.20 1.27 1.28 angle Rating NG NG NG NG NGretention Sand wedge DRY Initial velocity (m/s) 9 9 9 9 9 evaluationLaunch angle (deg) 34.7 35.3 35.1 35.1 34.8 (HS, 10 m/s) Spin rate (rpm)3,636 3,454 3,517 3,532 3,579 WET Initial velocity (m/s) 9 8 9 9 9Launch angle (deg) 44.7 43.6 41.8 43.7 42.2 Spin rate (rpm) 1,888 2,0042,322 2,029 2,252 Spin rate Ratio 0.52 0.58 0.66 0.57 0.63 retentionRating NG NG NG NG NG Launch Ratio 1.29 1.24 1.19 1.25 1.21 angle RatingNG NG good NG NG retention

As is apparent from the results in Table 4, the golf balls in Examples 1to 4 according to the present invention satisfy both of the conditions“Spin W/Spin D≥0.70” and “Ang W/Ang D<1.20” at head speeds of both 20m/s and 10 m/s. As a result, these golf balls has a good controllabilityunder wet conditions. By contrast, the golf balls in ComparativeExamples 1 to 6 failed to satisfy both of the conditions “Spin W/SpinD≥0.70” and “Ang W/Ang D<1.20” at these head speeds. As a result, thehad a poor controllability under wet conditions.

Japanese Patent Application No. 2019-231164 is incorporated herein byreference. Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings, it is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A golf ball comprising a core and a cover, wherein the ball has aspin rate and a launch angle on approach shots at a head speed (HS) of20 m/s that satisfy formulas (1) and (2) below:Spin W/Spin D≥0.70   (1)Ang W/Ang D<1.20   (2), where Spin D is the spin rate (rpm) under dryconditions, Spin W is the spin rate (rpm) under wet conditions, Ang W isthe launch angle (°) under wet conditions and Ang D is the launch angle(°) under dry conditions.
 2. A golf ball comprising a core and a cover,wherein the ball has a spin rate and a launch angle on approach shots ata head speed (HS) of 10 m/s that satisfy formulas (1) and (2) below:Spin W/Spin D≥0.70   (1)Ang W/Ang D<1.20   (2), where Spin D is the spin rate (rpm) under dryconditions, Spin W is the spin rate (rpm) under wet conditions, Ang W isthe launch angle (°) under wet conditions and Ang D is the launch angle(°) under dry conditions.
 3. The golf ball of claim 1, wherein the coverhas an outermost layer on which a coating layer is formed, which coatinglayer is formed of a coating composition composed primarily of aurethane coating containing both a base resin comprising a polyesterpolyol and a curing agent comprising a polyisocyanate.
 4. The golf ballof claim 3, wherein the coating composition includes from 0.1 to 10parts by weight of a water-repellent additive per 100 parts by weight ofthe base resin, inclusive of a solvent.
 5. The golf ball of claim 4,wherein the water-repellent additive is a fluorine-based water repellentor an acrylic additive.
 6. The golf ball of claim 4, wherein thewater-repellent additive is an acrylic additive comprising asilicone-modified acrylate.
 7. The golf ball of claim 4, wherein thewater-repellent additive is a fluorine-based water repellent comprisinga fluorine-based polymer having an alkyl group chain length of 7 orless.
 8. The golf ball of claim 3, wherein hexamethylene diisocyanate isused as the polyisocyanate, with both an isocyanurate and an adduct ofthe hexamethylene diisocyanate being used together.
 9. The golf ball ofclaim 8, wherein the mixing ratio of the isocyanurate and the adduct ofhexamethylene diisocyanate, expressed as the weight ratio“isocyanurate/adduct,” is from 95/5 to 40/60.